I won't pay twice

On the 28 of July in the morning I received a call from MDC consultant asking me to pay RCS account I told the consultant that I paid last year on the 4th of July in Standard bank with MBDLC . The account number was ***6 , and i still have the receipt pls check with your system propelyIt was R357,00 can you pla give me a break this is truly annoying and causing me trouble. I can't get a job because of this account my name still appears as blacklisted if they check for my credit records.